RFID (radio frequency identification) communication systems are used in many fields, for example security applications, access controls, payment systems, tagging and tracking items, etc. In this case, passive RFID transponders are integrated into chip cards or tags, for example, and are read or written to with the aid of an RFID reader. In this case, the RFID reader uses inductive coupling to provide the energy needed by the passive RFID transponder to process and transmit data. As a result of the weak coupling between the transponder antenna and the antenna of the reader, the signal to be detected on the reader side is considerably smaller than the carrier signal. The ratio of carrier signal to received signal is in the region of 80 dB, for example, which constitutes a great challenge for the reader.
On the side of the passive RFID transponder, the challenge is to transmit data with as little hardware complexity and energy consumption as possible and nevertheless to achieve data rates which are as high as possible.